Oil-saving, energy conservation and environmental protection are challenges for the whole human beings in the 21st century. The United Nations invited representatives of over 100 nationals to sign the “Kyoto Protocol” in Japan in Feb. 6, 2005, hoping that each country in the world obeyed the restriction on CO2 emission within a time limit to prevent the earth's environment and climate from continuously deteriorating. To do this, the first thing is the policy of energy conservation and carbon reduction.
The high oil price era came in August 2008, when the price of crude oil was as high as up to $150 per barrel, causing the upsurge in fuel cost of car, ship and airplane in each country of the world, the economic development to be shrouded in shadow, and even the price index of many countries to soar due to the oil price. At the same time, the ice layers in the earth's north and south poles have been gradually collapsing into the sea and the climate has been rapidly deteriorating, so many meteorologists and scientists continuously appeal to the whole world for obeying energy conservation and carbon reduction to salvage the disaster of human beings.
A hybrid car is thus presented to the public in view of the demand for oil saving and environmental protection. For example, according to the technique disclosed in U.S. Pat. No. 5,935,040, an internal combustion engine and a servomotor are provided in a car at the same time, with a very high capacity battery also provided for storing electric energy when the engine is running. After the amount of electric energy stored in the battery reaches a predetermined limit, the engine can be shut down and the moving of the car can still be driven only by the servomotor. Also, if necessary, the engine and the servomotor can operate simultaneously so as to provide a larger output of power.
However, the hybrid car requires a servomotor of larger horsepower to output a larger torque to transmit power to a transmission shaft, and requires a large capacity battery for supplying electric power for a long time. Therefore, the equipment cost is greatly increased. Further, it is quite difficult for designing and installation to assemble such a huge servomotor and battery into the limited space of the car.